Rock bolt with information display region

ABSTRACT

A rock bolt arranged for installation within a bore formed in rock strata includes an elongate shaft with the leading end for installation into the bore and a trailing end projecting from an open end of the bore. A locking nut is threadably attached to the trailing end and is arranged to display product information and the like at a display face. The display face is recessed axially into the nut to provide protection against damage to the display face that may otherwise render the information unreadable.

FIELD OF INVENTION

The present invention relates to a rock bolt for installation within abore formed in rock strata and in particular to a rock bolt with a nuthaving a recessed portion for displaying information.

BACKGROUND ART

Roof and wall support is vital in underground mining and tunnellingoperations. Tunnel walls and roofs are typically formed from rock stratathat requires reinforcement to prevent failure, fragmentation orcollapse. Typically, a bore hole is formed in the rock strata by adrilling operation and then the rock bolt is installed into theas-formed bore where it is secured to provide reinforcement againstmajor rock fracture and strata fragmentation.

Different forms of rock bolts have been developed including resin orcement grout bolts that are frictionally secured in the bore using aresin or grout introduced into the bore prior to the bolt which sets tolock the bolt into position. Mechanical friction rock bolts haveexpander mechanisms positioned towards a leading end that function toexpand radially within the bore to prevent axial withdrawal. Thetrailing end of resin, grout and mechanical friction rock boltstypically project a short distance outside of the bore and remainvisible. In some instances, the trailing end of the bolt is used forsupporting ancillary fixtures such as containment meshing (via meshingplates), mining services utilities, pipes, cables etc. In someinstallations, the projecting end of the rock bolt can be threaded forconnection of mechanical fixtures.

A locking nut at the trailing end of the rock bolt may be a blind nutwhich in the case of a mechanical friction bolt is configured to engagethe rearward end of the bar such that further rotation of the nutprovides a corresponding rotation of the bolt shaft to provideinstallation via a translated expansion of the expander mechanism.Typically, product information is stamped on an external exposed face ofthe locking nut that may include an alphanumeric code for materialtraceability, bolt ID etc. However, this exposed face is often damagedby the bolt installation driver tool as the bolt is hammered into thebore. Accordingly, such stamped information often becomes unreadable.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a rock boltconfigured to display information that is prevented from damage duringbolt installation into a receiving bore hole in the rock strata so as topreserve the information to be capable of being displayed after boltinstallation.

It is a specific objective to provide a locking nut for a rock boltadapted to carry relevant information such as bolt identification (ID),material traceability information, manufacturer information, rock bolttype information, codes, logos, trademarks and other indicia to bevisible to personnel within a mine tunnel where a rock bolt is installedfor example in a wall or roof The objectives are achieved by providing arock bolt having an axially rearward nut attached to an elongate shaftof the bolt with the nut having a recessed portion that in turn providesa display face that is axially recessed relative to an axiallyrearwardmost exposed face of the nut. As the display face is recessedaxially (relative to the rearward exposed face), the display face isprotected from the bolt driver tool and in particular the driver socketthat is typically positioned over and about the nut to deliver thepercussive hammering action.

Conventionally, bolt driver tools and in particular driver sockets areat least part tubular having a cylindrical inner cavity. Optionally, thenut of the rock bolt of the present invention is provided with arecessed portion having a diameter that is approximately equal to orless than a diameter of the internal cylindrical cavity of the driversocket such that no part of the driver socket is positioned in contactwith or extends over the recessed portion and in particular the axiallyrecessed display face. According to a preferred implementation, therecessed portion and the recessed display face are positioned centrallyat a rearward facing exposed face of the nut with the exposed face beingannular to extend around the recessed portion and the display face. Insuch an implementation, the driver socket and in particular an abutmentcontact area of the driver socket is adapted to sit into contact withthe annular exposed face and not to overlay onto the recessed portion.

According to a first aspect of the present invention there is provided arock bolt for installation within a bore formed in rock stratacomprising: an elongate shaft having a leading end for installation intothe bore and a threaded trailing end to project from an open end of thebore; an internally threaded nut attached at the trailing end to mount arock plate against a surface of the rock strata, the nut having anaxially forward facing contact face for positioning opposed to the rockplate and an axially rearward facing exposed face; characterised by: arecessed portion extending axially inward from the exposed face anddefining an axially rearward facing display face being axially recessedrelative to the exposed face.

Optionally, the nut is a blind or semi-blind nut optionally when usedwithin a mechanical friction bolt system. Optionally, the nut may benon-blind to comprise a through-bore internally threaded between a firstand second axial end, for example within a resin or cement grouted boltsystem. The thread may extend completely or partially the axial lengthof the nut.

Optionally, the exposed face is annular and the display face ispositioned centrally and surrounded by the exposed face. Optionally, thenut is semi-blind, the display face is annular and extends around acentral opening into an internal threaded cavity of the nut. Optionally,the nut may be semi-blind and comprise a non-circular recess wall. Wherethe nut is fully blind, the display face may be circular, polygonal andin particular hexagonal or heptagonal.

Optionally, the bolt further comprises a tab mounted within the recessedportion and having an axially rearward facing tab display face. The tabmay be disc-shaped, or at least part disc-shaped. Optionally, the tabmay be generally planar or may be mushroom-shaped having a forward and arearward facing face. The tab may comprise indicia provided at each ofthe forward and rearward faces. Accordingly, the tab may be positionedin two different orientations within the recessed portion. Optionally,the tab may be non-circular (e.g., hexagonal). Optionally, the tab maybe non-planar and may comprise a head part and a shaft extending fromthe head. Preferably, the shaft is capable of locating within an openingof a semi-blind nut.

Preferably, the bolt further comprises indicia provided at the displayface. The indicia at the display face of the nut may be additional toany indicia provided at the tab display face(s). Accordingly, theinformation at the display face of the nut may be the same or differentto the information provided on the display face(s) of the tab.

Optionally, an outside surface of the nut comprises a polygonal, squareor hexagonal cross sectional profile. Such a configuration provides anut that is conveniently engageable and drivable by conventional boltdrive apparatus having an engaging driver socket.

Preferably, the nut comprises threads at the outside surface. This isbeneficial for attachment of auxiliary fixtures to the nut with suchauxiliary fixtures having an internally threaded socket for thethreading onto the outside surface of the nut.

Optionally, the recessed portion comprises an undercut such that adiameter of the recessed portion increases in an axial direction fromthe exposed face. Optionally, the recessed portion may be provided withan adhesive, crimping, weld or at least one radial projection extendingradially to overlay at least a portion of the tab. Optionally, where therecessed portion comprises an undercut, the tab may be secured withinthe recessed portion by abutment underneath the undercut. Optionally,the recessed portion may be threaded such that the tab may be screwedinto the recessed portion via a suitable forked tool or other engagementtool.

Preferably, an axial thickness of the tab is less than an axial depth ofthe recessed portion. In particular, a thickness of the tab is less thana minimum axial depth of the recess portion, where the recessed portiondepth is non-uniform at the nut. Optionally, a distance by which thedisplay face is recessed axially relative to the exposed face is lessthan a radial wall thickness of the nut. Optionally, said distance isless than a thickness of an end wall of a semi-blind or fully blind nut.

Optionally, the rock bolt may be a resin, cement grouted or mechanicalfriction bolt or any other bolt with a nut.

BRIEF DESCRIPTION OF DRAWINGS

A specific implementation of the present invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings in which:

FIG. 1 is a partial cross sectional view of a mechanical friction rockbolt assembly configured for anchored mounting within a bore formedwithin rock strata according to a specific implementation of the presentinvention;

FIG. 2 is a cross sectional perspective view of a locking nut secured ata trailing end of the rock bolt of FIG. 1 according to the specificimplementation of the present invention;

FIG. 3 is a cross sectional perspective view of a locking nut accordingto a further specific implementation of the present invention securableto the trailing end of the rock bolt of FIG. 1;

FIG. 4 is a cross sectional perspective view of a further specificimplementation of a locking nut securable to the trailing end of therock bolt of FIG. 1;

FIG. 5 is a cross sectional perspective view of a bolt driver socketpositioned in contact with the locking nut of FIG. 4 to providepercussive driving of the rock bolt of FIG. 1 into a bore hole.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

The present locking nut is suitable for use with a variety of differenttypes of rock bolt including resin, cement grout and mechanical frictionrock bolts where the nut is attachable via cooperating screw threads toa trailing end of an elongate shaft of the rock bolt. The presentlocking nut according to its use with different types of rock bolt, maybe used to actuate an expander mechanism within a mechanical frictionrock bolt and/or to secure a rock or meshing plate against the rockstrata at the region around the bore hole within which the rock bolt ismounted. According to all the implementations, the present locking nutis internally threaded and adapted for releasable securing onto thethreaded trailing end of an elongate shaft extending through the rockbolt.

For the purposes of describing the aspects of the present invention, alocking nut configured for the display of information is described withreference to a mechanical friction bolt. In particular, and referring toFIG. 1, a friction rock bolt assembly 10 is configured for mounting andsecurement within a bore 36 extending within a rock strata 15. Thefriction bolt 10 is generally elongate being centred on longitudinalaxis 52 and comprises primarily an elongate tube 25 that is splitaxially; an expander mechanism indicated generally by reference 11; andan anchor mechanism indicated generally by reference 12. Expandermechanism 11 is mounted towards a leading end 16 of tube 25 whilstanchor mechanism 12 is positioned towards a trailing end 41 of tube 25.In particular, anchor mechanism 12 projects rearwardly from tube 25 andis positioned at and extends from an open end of bore 36 adjacent asurface 35 of the rock strata 15 that surrounds the bore open end.

Expander mechanism 11 may be formed from a pair of cooperating wedges14, 17. A first wedge 14 is formed generally as a collar having aninternal bore with radially inwardly facing threads to engage andcooperate with corresponding threads 20 provided at a first leading end21 of an elongate bar 22 that extends axially through tube 25 from tubetrailing end 41 to tube leading end 16. First wedge 14 is accordinglyaxially adjustable at bar 22 via the respective threads. Second wedge 17is mounted rigidly to an internal facing surface 26 of tube 25 at aposition towards tube leading end 16. The first and second wedges 14, 17each comprise a respective engaging surface 18, 19 aligned transverse toaxis 52. Accordingly, by linear axial adjustment of first wedge 14 alongbar 22, engaging surface 18 of first wedge 14 abuts engaging surface 19of second wedge 17 so as to force the first wedge 14 radially outwardfrom axis 52 and against tube internal surface 26. The radial expansionof expander mechanism 11 acts to force and deform tube 25 radiallyoutward against the internal facing surface of bore 36 to lock thefriction bolt assembly 10 within the bore 36.

Linear axial movement of first wedge 14 is provided by anchor mechanism12 that comprises an internally threaded nut 32 mounted to a secondtrailing end 40 of bar 22. Accordingly, rotation of nut 32 about axis 52provides a corresponding rotation of bar 22 that, in turn, pulls thefirst wedge 14 towards tube trailing end 41 (via threads 20) to providethe radial expansion force. Anchor mechanism 12 further comprises awasher 31 (alternatively termed a gasket) having a central aperture 33to sit about and around bar 22 at trailing end 40. Gasket 31 is formednon-integrally with nut 32, tube 25 and other components of the boltassembly 10 so as to be an independent component. Gasket 31 projectsradially outward from bar 22 and tube 25 such that an abutment surface37 that is orientated generally axially towards tube leading end 16extends radially outward beyond a radially external facing surface 54 oftube 25. Gasket 31 and surface 37 extend radially outward beyond tubeexternal surface 54 by a distance that is approximately equal to orgreater than a corresponding radial distance by which gasket 31 projectsradially inward from tube internal surface 26 towards bar 22 that iscentred on axis 52. As will be appreciated, the distance by the gasket31 extends radially beyond the tube wall may be varied and selected tosuit specific applications. Accordingly, gasket 31 provides a radiallyoutward extending flange at the tube trailing end 41 and bar trailingend 40. Gasket 31 accordingly projects radially outward beyond thediameter of bore 36 (formed within the rock strata 15) such that atleast a radial outer region of abutment surface 37 is capable of beingbraced, either directly or indirectly, against the rock strata surface35 that surrounds radially the bore open end.

According to the specific implementation, the friction rock boltassembly 10 comprises a rock plate indicated generally by reference 30that is formed as a profiled generally annular gasket having a radiallyouter portion and a corresponding radially inner portion. The radiallyouter portion comprises a generally annular (or in other instancesrectangular) abutment surface 23 configured to sit against the rockstrata surface 35 whilst the inner portion terminates as an annular edge48 that defines a central hole having a diameter slightly greater than adiameter of tube 25 but less than a corresponding diameter of gasket 31.In particular, the radially inner edge 48 of rock plate 30 is configuredto abut gasket surface 37 such that gasket 31 is braced against the rockstrata surface 35 via rock plate 30. Accordingly, gasket 31 projectsradially outward from tube 25 to provide an appropriate radial overlapbetween the radially inner portion of rock plate 30 and a radially outerportion of gasket 31 in turn allowing gasket 31 to be braced againstrock plate 30 which is, in turn, braced against rock strata surface 35either directly or via an intermediate meshing sheet (not shown) toprovide containment of the rock strata at a tunnel wall or roof. Tubetrailing end 41 according to the specific implementation, is devoid of aring or collar (not shown) positioned externally at tube externalsurface 54. Such a ring or collar may be welded to trailing end 41 toprovide a region of abutted mating with the radially inner edge 48 ofrock plate 30. According to further embodiments, gasket 31 may beconfigured to sit directly against the rock strata 15 via respectiveabutment between abutment surface 37 and rock surface 35.

Referring to FIG. 2, nut 32 comprises an outside surface 42 having apolygonal and in particular hexagonal cross sectional profile. Threads39 are provided at outer surface 42 so as to provide mounting ofauxiliary fixings to nut 32 either before or once bolt 10 is mounted andsecured in position within bore 36. Nut 32 comprises a generallycylindrical internal cavity 28 defined by a radially inward facing innersurface 55 onto which threads 34 are formed. Threads 34 extendsubstantially the full axial length of nut 32 between an axially forwardfacing annular contact face 13 and a semi-blind innermost end of cavity28 defined by an end wall 43. An opening 50 is formed within end wall43. However, according to further implementations, end wall 43 may besolid across the full diameter so as to define a fully blind nut 32. Anaxially rearward end of nut 32 is defined by an axially rearward facingannular exposed face 38 that represents an axial end of nut wall 27 thatdefine internal cavity 28. The rearward end of nut 32 is further definedby end wall 43 and opening 50.

According to the specific implementation, a recessed portion indicatedgenerally by reference 45 is provided at the axially rearward end of nut32 at the region of end wall 43. In particular, the central region ofexposed face 38 is recessed axially inward such that a display face 29(that represents an axially rearward facing surface of end wall 43) isrecessed axially relative to exposed face 38. Display face 29 is annularto surround circular opening 50 and is in turn surrounded by the annularexposed face 38. According to the specific implementation, an axialdistance by which display face 29 is recessed axially relative toexposed face 38 is less than a thickness of nut wall 27 and inparticular is less than 50%, 40%, 30% of the wall thickness and may bein the range 5 to 30% or 5 to 20% of a thickness of nut wall 27.

Referring to FIG. 4, recessed portion 45 may be formed with an undercut49 such that a diameter of the recess from exposed face 38 increases inthe axial direction from exposed face 38 towards end wall 43. Accordingto the embodiments of FIGS. 2 and 4, a display tab 47 having a disc-likeconfiguration is capable of being mounted within recessed portion 45.According to the embodiment of FIG. 4, tab 47 may be secured by abutmentcontact underneath the undercut 49 that forms a securing lip around theperimeter of tab 47.

Accordingly, tab 47 may be formed from a resiliently deformable and/orflexible material such as a metal or a polymer. Accordingly, tab 47 issecured in position by frictional contact between undercut 49 and wall43 and is positioned in contact with and overlaying display face 29(FIG. 2). A thickness of tab 47 is less than the axial depth of recessedportion 45 such that tab display face 46 is aligned coplanar orpreferably is recessed relative to exposed face 38.

The recessed display face 29 at end wall 43 is capable of displayinginformation relative to the rock bolt 10, the region of installation,the manufacturer of the components described herein, the installer orother relevant information including materials, dates, product codes,logos, trademarks etc. In particular, display face 29 is capable ofdisplaying indicia that may be marked, printed, etched, stamped or inother ways adhered to face 29. As will be appreciated, the same orsimilar information may be provided at tab display face 46 with suchinformation being additional or alternative to the information displayedat end wall display face 29.

The present arrangement of nut 32 is advantageous as detailed withreferent to FIG. 5 by avoiding damage to the display faces 29, 46 by abolt driver tool and in particular driver socket 51 that is brought intocontact with nut 32 for percussive hammering of the rock bolt 10 intothe bore 36. In particular, driver socket 51 comprises an annularleading end face 53 for abutment contact against gasket 31. An internalcavity 57 extends axially from end face 53. A shoulder 60 projectsradially inward at an axially inner end of cavity 57 to define anannular cavity end face 56. A generally cylindrical bore 58 extendsaxially rearward from cavity end face 56 and is defined by a radiallyinward facing surface 59. Preferably, a diameter of recessed portion 45and in particular display face 29 is approximately equal to or less thana diameter of driver socket bore 58 such that no part of driver socket51 is capable of abutment contact with display face 29 of wall 43 and/ortab display face 46. As will be appreciated, driver socket 51 may varyin design and may not include central bore 58 such that cavity end face56 is circular and is capable of being brought into full abutmentcontact against the rearward facing end face of nut 32. Via the recessedportion 45, driver socket end face 56 abuts only the exposed face 38 soas to protect and preserve the information (indicia) 44 provided at therespective display faces 29, 46.

A further embodiment of the present invention is described referring toFIG. 3 in which nut 32 is not blind or semi-blind and that internalcavity 28 (of FIG. 2) extends the full axial length of nut 32 betweencontact face 13 and the axially rearwardmost exposed face 38. Accordingto this further embodiment, recessed portion 45 is annular and isrecessed into exposed face 38 as an annular channel or groove so as toradially divide exposed face 38 into an annular inner face 38 b and anannular outer face 38 a. Information 44 (not shown in the embodiment ofFIG. 3) is provided at the display face 29 as described referring toFIG. 2. Additionally, an annular tab 46 of the type described referringto FIG. 4 may be mounted within the annular recessed portion 45 via theoptional anchorage mechanisms described referring to the embodiment ofFIG. 4. As will be appreciated, important aspects of all embodiments ofthe present invention are that display face 29 is recessed axiallyrelative to an axially rearwardmost exposed face 38, 38 a, 38 b so as toavoid damaging abutment contact with driver socket end face 56. Thisrecessed arrangement further protects and preserves the displayedinformation from damage by the attachment of auxiliary fixtures such asrock plates, mining services, pipes, cables, eyelets, meshing platesfixings etc.

1. A rock bolt arranged for installation within a bore formed in rockstrata, the rock bolt comprising: an elongate shaft having a leading endfor installation into the bore and a threaded trailing end arranged toproject from an open end of the bore; an internally threaded nutattached at the trailing end arranged to mount a rock plate against asurface of the rock strata, the nut having an axially forward facingcontact face arranged for positioning opposed to the rock plate and anaxially rearward facing exposed face; and a recessed portion extendingaxially inward from the exposed face and defining an axially rearwardfacing display face being axially recessed relative to the exposed face.2. The rock bolt as claimed in claim 1, wherein the nut is a blind orsemi-blind nut.
 3. The rock bolt as claimed in claim 1, wherein theexposed face is annular and the display face is positioned centrally andsurrounded by the exposed face.
 4. The rock bolt as claimed in claim 3,wherein the nut is semi-blind and the display face is annular andextends around a central opening into an internal threaded cavity of thenut.
 5. The rock bolt as claimed in claim 1, further comprising a tabmounted within the recessed portion and having an axially rearwardfacing tab display face.
 6. The rock bolt as claimed in claim 1, furthercomprising indicia provided at the display face.
 7. The rock bolt asclaimed in claim 1, wherein an outside surface of the nut has apolygonal, square or hexagonal cross sectional profile.
 8. The rock boltas claimed in claim 7, wherein the nut includes threads at the outsidesurface.
 9. The rock bolt as claimed in claim 1, wherein the recessedportion includes an undercut such that a diameter of the recess portionincreases in an axial direction from the exposed face.
 10. The rock boltas claimed in claim 9, further comprising a tab mounted within therecessed portion and having an axially rearward facing tab display face,wherein the tab is secured within the recessed portion by abutmentunderneath the undercut.
 11. The rock bolt as claimed in claim 5,wherein the tab has an axial thickness less than an axial depth of therecessed portion.
 12. The rock bolt as claimed in claim 5, wherein thetab is secured within the recessed portion by an adhesive, crimping,weld or at least one radial projection extending radially to overlay atleast a portion of the tab.
 13. The rock bolt as claimed in claim 1,wherein a distance by which the display face is recessed axiallyrelative to the exposed face is less than a radial wall thickness of thenut.
 14. The rock bolt as claimed in claim 13, wherein the distance bywhich the display face is recessed axially relative to the exposed faceis less than half a radial wall thickness of the nut.
 15. The rock boltas claimed in claim 1, comprising a resin, cement grouted or mechanicalfriction bolt.